Crossea biconica

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Crossea biconica
Crossea biconica 001.jpg
Original drawing of a shell of Crossea biconica
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Clade: Vetigastropoda
Order: Trochida
Superfamily: Trochoidea
Family: Conradiidae
Genus: Crossea
Species:
C. biconica
Binomial name
Crossea biconica
Hedley, 1902

Crossea biconica is a species of small sea snail or micromollusc, a marine gastropod mollusc in the family Conradiidae. [1]

In biology, a species ( ) is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. While these definitions may seem adequate, when looked at more closely they represent problematic species concepts. For example, the boundaries between closely related species become unclear with hybridisation, in a species complex of hundreds of similar microspecies, and in a ring species. Also, among organisms that reproduce only asexually, the concept of a reproductive species breaks down, and each clone is potentially a microspecies.

Sea snail common name for snails that normally live in saltwater

Sea snail is a common name for snails that normally live in salt water, in other words marine gastropods. The taxonomic class Gastropoda also includes snails that live in other habitats, such as land snails and freshwater snails. Many species of sea snails are edible and exploited as food sources by humans.

Family is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy; it is classified between order and genus. A family may be divided into subfamilies, which are intermediate ranks between the ranks of family and genus. The official family names are Latin in origin; however, popular names are often used: for example, walnut trees and hickory trees belong to the family Juglandaceae, but that family is commonly referred to as being the "walnut family".

Contents

Description

(Original description by Charles Hedley) The height of the shell attains 1.7 mm, its diameter 1.6 mm. The minute but solid, white shell has a biconical shape. Its base is greatly produced, the periphery keeled. The four whorls are somewhat turreted.

Charles Hedley Australian zoologist

Charles Hedley was a naturalist, specifically a malacologist. Born in Britain, he spent most of his life in Australia. He was the winner of the 1925 Clarke Medal.

Whorl (mollusc)

A whorl is a single, complete 360° revolution or turn in the spiral growth of a mollusc shell. A spiral configuration of the shell is found in of numerous gastropods, but it is also found in shelled cephalopods including Nautilus, Spirula and the large extinct subclass of cephalopods known as the ammonites.

Sculpture  : The first and second whorls are smooth, the third comparatively coarsely cancellated, the fourth contains dense fine spiral cords crossed by fainter growth lines which tend to bead the interstices. The base is two-thirds of the total height. The wide and deep umbilicus is bordered by a conspicuous ridge, and has an elevated funicle winding within. The oblique aperture is rhomboidal, channelled by the umbilical ridge, and with a gutter at the termination of the funicle. A heavy outstanding varix occurs a short distance behind the aperture.

Sculpture (mollusc)

Sculpture is a feature of many of the shells of mollusks. It is three-dimensional ornamentation on the outer surface of the shell, as distinct from either the basic shape of the shell itself or the pattern of colouration, if any. Sculpture is a feature found in the shells of gastropods, bivalves, and scaphopods. The word "sculpture" is also applied to surface features of the aptychus of ammonites, and to the outer surface of some calcareous opercula of marine gastropods such as some species in the family Trochidae.

Umbilicus (mollusc)

The umbilicus of a shell is the axially aligned, hollow cone-shaped space within the whorls of a coiled mollusc shell. The term umbilicus is often used in descriptions of gastropod shells, i.e. it is a feature present on the ventral side of many snail shells, including some species of sea snails, land snails, and freshwater snails.

Aperture (mollusc) The main opening of the shell, where the head-foot part of the body of the animal emerges

The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where the head-foot part of the body of the animal emerges for locomotion, feeding, etc.

The small size, produced base, and wide umbilicus are characters which distinguish this from other Australian members of the genus. [2]

Distribution

This marine species is endemic to Australia. It is found off the Northern Territory and Queensland

Northern Territory federal territory of Australia

The Northern Territory is an Australian territory in the central and central northern regions of Australia. It shares borders with Western Australia to the west, South Australia to the south, and Queensland to the east. To the north, the territory looks out to the Timor Sea, the Arafura Sea and the Gulf of Carpentaria, including Western New Guinea and other Indonesian islands. The NT covers 1,349,129 square kilometres (520,902 sq mi), making it the third-largest Australian federal division, and the 11th-largest country subdivision in the world. It is sparsely populated, with a population of only 246,700, making it the least-populous of Australia's eight states and major territories, with fewer than half as many people as Tasmania.

Queensland North-east state of Australia

Queensland is the second-largest and third-most populous state in the Commonwealth of Australia. Situated in the north-east of the country, it is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean. To its north is the Torres Strait, with Papua New Guinea located less than 200 km across it from the mainland. The state is the world's sixth-largest sub-national entity, with an area of 1,852,642 square kilometres (715,309 sq mi).

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References